DESCRIPTION: (Applicant's Description) The long-term goal of this research proposal is to gain an understanding of the molecular events associated with the modulation of N-type Ca2+ channels by Gbetagamma subunits. The main hypothesis to be tested is that the subunit composition of the Gbetagamma dimer, i.e., specific combinations of Gbeta and Ggamma confer specificity in regard to voltage-dependent N-type Ca2+ channel modulation. Accordingly, the specific aims are 1) to identify which G protein beta subunit produces voltage-dependent N-type Ca2+ channel inhibition in rat sympathetic neurons; 2) to determined which G protein betagamma combinations confer specificity for voltage-dependent N-type Ca2+ channel modulation; and 3) to identify the G protein beta and gamma subunits that are natively expressed in rat sympathetic neurons by employing the Western blotting method. By employing electrophysiological, molecular, and biochemical methods, the role of the Gbetagamma composition in modulation of Ca2+ channels will be delineated and better understood. Voltage-dependent modulation of N-type Ca2+ channels has been demonstrated in a wide variety of neurons from both the central and peripheral nervous system. Although most studies are performed on the neuron soma, there is evidence from direct studies of nerve terminals to support the idea that this form of modulation plays an important role in presynaptic mechanisms of synatic transmission. Thus there is substantial interest in furthering our understanding of the molecular events which contribute to N-type Ca2+ channel modulation.